Postoperative neurological deficits in segmental spinal instrumentation. A study using spinal cord monitoring

Delayed Postoperative Spinal Cord Injury with Complete Paralysis After Adolescent Idiopathic Surgery: A Case Report

CASE

We report a 14-year-old girl with adolescent idiopathic scoliosis who experienced bilateral lower extremity paralysis related to postoperative hypotension 10 hours after posterior spinal fusion. She returned to the operating room for spinal cord decompression and hardware removal. Six weeks later, reinstrumentation was performed, and complete neurologic recovery was achieved.

CONCLUSION

Delayed presentation of neurologic injury after scoliosis surgery is particularly uncommon. Close postoperative monitoring, with an emphasis on hypotensive etiologies and a low threshold to remove the instrumentation, is essential to rapidly diagnose and treat these catastrophic events.

Efficacy of polyester bands placed under the transverse vertebral process for the correction of adolescent idiopathic scoliosis : A case series of 105 patients with a minimum of 24 months follow-up

PURPOSE

To report an original technique for the surgical correction of adolescent idiopathic scoliosis (AIS) based on hybrid construct using polyester bands placed under the thoracic transverse processes.

METHODS

We reviewed 105 patients operated between 2013 to 2017 for AIS with a minimum of 2 years follow-up. Clinical and radiological data, including 2D measurements of scoliosis parameters preoperatively, and at 3- and 24-months postoperatively were analyzed. Radiological analysis was performed by two independent observers using KEOPS (Smaio, Lyon-France, CE 2014) database.

RESULTS

Mean age was 14.6 ± 2 years. Mean follow-up was 23.7 ± 1.2 months. Most curves were classified as Lenke-1 (78%). The average number of vertebra involved in the construct was 10.9 ± 1.3 (range 7-13). A mean of 12.8 implants were used per construct (mean implant density 0.59). The number of subtransverse bands placed averaged 3 (range 1-5 bands). The mean frontal Cobb angle decreased from 57.9 to 21.2 ° (p < 0.05) postoperatively. The average T4-T12 kyphosis increased from 20.2°to 32.4° (p < 0.05) postoperatively and no loss of correction was observed at 2 years follow-up. We encountered one case of transverse process fracture intraoperativley. No neurological complications were observed. In the postoperative period, 4 cases were diagnosed with distal junctional failure, three of which required an extension of the construct, while the fourth case was treated by bracing.

CONCLUSIONS

The use of subtransverse band is an efficient and safe method for the surgical correction of AIS. This technique incorporates technical ease (minimal risk of neurological injury), provides good frontal correction and restores thoracic kyphosis. Results are maintained over a two-year period.

Neurophysiological monitoring of spinal cord function during spinal deformity surgery: 2020 SRS neuromonitoring information statement

The Scoliosis Research Society has developed an updated information statement on intraoperative neurophysiological monitoring of spinal cord function during spinal deformity surgery. The statement reviews the risks of spinal cord compromise associated with spinal deformity surgery; the statement then discusses the various modalities that are available to monitor the spinal cord, including somatosensory-evoked potentials, motor-evoked potentials, and electromyographic (EMG) options. Anesthesia considerations, the importance of a thoughtful team approach to successful monitoring, and the utility of checklists are also discussed. Finally, the statement expresses the opinion that utilization of intraoperative neurophysiological spinal cord monitoring in spinal deformity surgery is the standard of care when the spinal cord is at risk.

Sublaminar polyester band fixation construct in the treatment of neuromuscular scoliosis

PURPOSE

Multiple fixation techniques exist for treating progressive neuromuscular scoliosis including pedicle screws, sublaminar bands/wires, hooks or a combination of instruments. Most sublaminar band constructs are supplemented with pedicle screws, hooks and/or sublaminar wires particularly at the top of the construct. There are no studies to date that describe an all/predominant sublaminar band construct. The purpose of this study was to investigate the outcomes of a sublaminar polyester band construct to treat neuromuscular scoliosis.

METHODS

A retrospective review was conducted of 32 cases of neuromuscular scoliosis treated with posterior spinal fusion using a sublaminar band construct between 2013 and 2016 by a single surgeon at a single centre. Preoperative, immediate postoperative and two-year follow-up radiographs and clinical records were reviewed. Sagittal, coronal and pelvic obliquity correction was measured. Blood loss, length of surgery and complications were recorded.

RESULTS

In all, 29 patients were included. Mean postoperative coronal plane correction was 57% (0% to 92%) and maintained at two-year follow-up. Mean sagittal balance was 2.3 cm (-2.5 to 6.4). Mean lumbar lordosis angle decreased by 7° (44° to 37°). Mean thoracic kyphosis angle increased by 9° (23° to 32°). Mean pelvic obliquity decreased by 50% (from 15° to 7°). There were four major complications (14%) and eight minor complications (21%). Mean blood loss was 1304 cc (250 cc to 2450 cc).

CONCLUSION

Sublaminar polyester band fixation constructs provide a viable option in correction of deformity in patients with neuromuscular scoliosis with comparable outcomes with what is reported with other constructs.

LEVEL OF EVIDENCE

V.

Sublaminar banding as an adjunct to pedicle screw-rod constructs: a review and technical note on novel hybrid constructs in spinal deformity surgery

Sublaminar implants that encircle cortical bone are well-established adjuncts to pedicle screw-rod constructs in pediatric deformity surgery. Sublaminar bands (SLBs) in particular carry the advantage of relatively greater bone contact surface area as compared to wires and pullout loads that are independent of bone mineral density, in contrast to pedicle screws. Whereas the relevant technical considerations have been reported for pediatric deformity correction, an understanding of the relative procedural specifics of these techniques is missing for adult spinal deformity (ASD), despite several case series that have used distinct posterior tethering techniques for proximal junctional kyphosis prevention. In this paper, the authors summarize the relevant literature and describe a novel technique wherein bilateral tensioned SLBs are introduced at the nonfused proximal junctional level of long-segment ASD constructs.

Treatment of adult thoracolumbar spinal deformity: past, present, and future

Care of the patient with adult spinal deformity (ASD) has evolved from being primarily supportive to now having the ability to directly treat and correct the spinal pathology. The focus of this narrative literature review is to briefly summarize the history of ASD treatment, discuss the current state of the art of ASD care with focus on surgical treatment and current challenges, and conclude with a discussion of potential developments related to ASD surgery.In the past, care for ASD was primarily based on supportive measures, including braces and assistive devices, with few options for surgical treatments that were often deemed high risk and reserved for rare situations. Advances in anesthetic and critical care, surgical techniques, and instrumentation now enable almost routine surgery for many patients with ASD. Despite the advances, there are many remaining challenges currently impacting the care of ASD patients, including increasing numbers of elderly patients with greater comorbidities, high complication and reoperation rates, and high procedure cost without clearly demonstrated cost-effectiveness based on standard criteria. In addition, there remains considerable variability across multiple aspects of ASD surgery. For example, there is currently very limited ability to provide preoperative individualized counseling regarding optimal treatment approaches (e.g., operative vs nonoperative), complication risks with surgery, durability of surgery, and likelihood of achieving individualized patient goals and satisfaction. Despite the challenges associated with the current state-of-the-art ASD treatment, surgery continues to be a primary option, as multiple reports have demonstrated the potential for surgery to significantly improve pain and disability. The future of ASD care will likely include techniques and technologies to markedly reduce complication rates, including greater use of navigation and robotics, and a shift toward individualized medicine that enables improved counseling, preoperative planning, procedure safety, and patient satisfaction.Advances in the care of ASD patients have been remarkable over the past few decades. The current state of the art enables almost routine surgical treatment for many types of ASD that have the potential to significantly improve pain and disability. However, significant challenges remain, including high complication rates, lack of demonstrated cost-effectiveness, and limited ability to meaningfully counsel patients preoperatively on an individual basis. The future of ASD surgery will require continued improvement of predictability, safety, and sustainability.

Management of Adolescent Idiopathic Scoliosis: Institutional Experience, Integration into Neurosurgical Practice, and Impact on Resident Training

OBJECTIVE

Management of adolescent idiopathic scoliosis (AIS) in neurosurgery residency training may have a significant impact on resident experience, even though few trainees are likely to pursue careers in the field of AIS. The impact of this exposure on resident knowledge in adult spinal disease management is the subject of our retrospective analysis.

METHODS

An analysis was performed of all adolescent patients undergoing surgical correction of spinal deformity between 2006 and 2016. Patient characteristics, including age at operation, Cobb angles, length of stay, operative time, blood loss, and complications, were collected. Objective benchmarks were created for resident education in the management of AIS. A survey was sent to the last 7 years of graduates to assess the impact of exposure to AIS during neurosurgery training on their current practice.

RESULTS

Nine male and 37 female patients ages 11 to 22 years were identified. Neurosurgical residents assisted in all procedures without fellows or surgical assistants. Average operative time was 336 minutes (range, 215-575 minutes), and blood loss per procedure was 603 mL (range, 200-4000 mL). The average Cobb angle correction was 72.2% (range, 35.3%-90.9%). Zero of the past 7 graduates currently treat AIS surgically. All 7 graduates agreed that exposure to AIS during residency enhanced their knowledge of adult spinal disease management.

CONCLUSIONS

Treatment of AIS by surgeons with specialized training can be effective and safe. Resident exposure to these patients enhances their understanding of spinal biomechanics and deformity correction, which is applicable to treating AIS and adult spinal deformity.

Influence of Intraoperative Neuromonitoring on the Outcomes of Surgeries for Pediatric Scoliosis in the United States

BACKGROUND

Intraoperative neuromonitoring (IONM) is used to detect impending neurologic damage during complex spinal surgeries. Although IONM is increasingly used during pediatric scoliosis surgeries in the United States, the effect of IONM on the outcomes of such surgeries at a national level is unclear.

METHODS

Using National Inpatient Sample (NIS) from 2009 to 2012, 32,305 spinal fusions performed in children 18 years old or younger of age with scoliosis were identified using ICD-9 procedure and diagnosis codes. IONM was identified using the ICD-9 procedure code 00.94. The effects of IONM use on length of stay (LOS), discharge disposition, hospital charges, and in-hospital complications were assessed using multivariate regression analysis adjusting for patient and hospital characteristics.

RESULTS

IONM was used in 5,706 (18%) of the surgeries. IONM was associated with increased home discharge (adjusted odds ratio [AOR] = 1.25 [95% confidence interval 1.10-1.40], p = .001). There was no difference in LOS (p = .096) and hospital charges (p = .750). Neurologic complications were noted in 52 (0.9%) surgeries using IONM and 368 (1.4%) surgeries without IONM (p = .005). Although IONM use trended toward lower risk of neurologic complications in multivariate analysis, it failed to achieve statistical significance (AOR = 0.77 [0.57-1.04], p = .084).

CONCLUSIONS

Reported use of IONM in this database was significantly less compared with other databases, suggesting that IONM might be underreported in the NIS database. Nevertheless, in this database, IONM was significantly associated with increased home discharge. Hospital charges and LOS were not affected by IONM. There was a trend toward lower risk of neurologic complications with IONM use, though this finding was not statistically significant.

Prediction of Scoliosis Curve Correction Using Pedicle Screw Constructs in AIS: A Comparison of Fulcrum Bend Radiographs and Traction Radiographs Under General Anesthesia

STUDY DESIGN

Retrospective radiographic review.

OBJECTIVES

Our objectives were to (1) compare the ability of fulcrum bend radiographs and traction radiographs under general anesthesia to predict correction of adolescent idiopathic scoliosis (AIS) using pedicle screw only constructs and (2) compare the fulcrum bend correction index (FBCI) with a new measurement: the traction correction index (TCI).

METHODS

This is a retrospective radiographic review of 80 AIS patients (62 female and 18 male), who underwent scoliosis correction with pedicle screw only constructs. The mean age at surgery was 14 years (range 9-20 years). Radiographic analysis was carried out on the preoperative and immediate postoperative posteroanterior standing radiographs and the preoperative fulcrum bend radiographs and traction radiographs under general anesthesia. FBCI is calculated by dividing the correction rate by the fulcrum flexibility and TCI is calculated by dividing the correction rate by the traction flexibility.

RESULTS

Preoperative mean Cobb angle of 63.9° was corrected to 25.8° postoperatively. The mean fulcrum bending Cobb angle was 37.6° and traction Cobb angle was 26.6°. The mean fulcrum flexibility was 41.1%, traction flexibility 58.4%, and correction rate 59.6%. The median FBCI was 137% and TCI was 104.3%.

CONCLUSIONS

When comparing fulcrum bend and traction radiographs, we found the traction radiographs to be more predictive of curve correction in AIS using pedicle screw constructs. TCI takes into account the curve flexibility better than FBCI.

Risk factors and clinical impact of perioperative neurological deficits following thoracolumbar arthrodesis

Objectives:

The rates of arthrodesis performed in the United States and globally have increased tremendously in the last 10–15 years. Amongst the most devastating complications are neurological deficits including spinal cord injury, nerve root irritation, and cauda equine syndrome. The primary purpose of this study is to understand the risk factors for perioperative neurological deficits in patients undergoing thoracolumbar fusion.

Patients and methods:

Data from the Nationwide Inpatient Sample between the years of 1999–2011 was analyzed. Patients were between the ages of 18 and 80 who had thoracolumbar fusion. Excluded were patients who underwent the procedure as a result of trauma or a malignancy. A list of covariates, including demographic variables, preoperative and postoperative variables that are known to increase the risk of perioperative neurological deficits were compiled. Statistical analysis utilized univariate and multivariate logistic regression for comparisons between these covariates and the proposed outcomes.

Results:

The analysis of 37,899 patients yielded an overall rate of perioperative neurological deficits and mortality of 1.20% and 0.27%, respectively. Risk factors for perioperative neurological deficits included increasing age (OR 1.023 95% CI 1.018–1.029), Van Walraven 5–14 (OR 1.535 95% CI 1.054–2.235), and preoperative paralysis (OR 2.551 95% CI 1.674–3.886). Furthermore, the data showed that being 65 years old or older doubled the risk for perioperative deficit (OR 1.655, CI 1.248–2.194, p < 0.001).

Conclusions:

This population based study found that increasing age, higher comorbid burden, and preoperative paralysis increased the risk of perioperative neurological deficits while female gender and hypertension were found to be protective.

Late neurological complications due to laminar hook compression in idiopathic scoliosis surgery

Introduction

To provide a review of unusual neurological complications occurring years after spinal instrumentation surgery.

Case Presentation

The authors analyzed the cases of three patients with adolescent idiopathic scoliosis who presented with delayed neurological symptoms (later than 12 months postoperatively) following spinal deformity surgery using Texas Scottish Rite Hospital (TSRH) hook-rod instrumentation. One case presented with conus medullaris syndrome while the last two were rare cases of posterior cord syndrome due to a dislodged laminar hook at the thoracolumbar transition.

Discussion

In all three cases, the neurological symptoms were due to direct laminar hook compression. Metallosis was observed extra-spinally around the hook-rod construct but not at the sublaminar site. The dislodged laminar hook responsible for the symptoms was situated at the concavity of the curve with the blade-tip pointing downwards. Symptomatic improvement was observed in all patients following complete hardware removal. Conscientious long-term follow-up of patients undergoing posterior spinal fusion (PSF) for adolescent idiopathic scoliosis (AIS) is important in order to recognize late neurological deficits directly related to instrumentation. Anamnesis and physical examination are key for initial assessment and diagnosis, while myelography and computed tomography (CT) images are of great help to confirm the site of spinal compression. Removal of the dislodged laminar hooks after PSF with TSRH instrumentation in AIS cases can potentially improve neurological symptoms.

Perioperative Neurologic Complications in Adult Spinal Deformity Surgery: Incidence and Risk Factors in 564 Patients

STUDY DESIGN

Prognostic study-case controlled.

OBJECTIVE

Describe the rate of neurologic complications in adult spinal deformity surgery and describe the effect of these complications on clinical outcomes.

SUMMARY OF BACKGROUND DATA

The incidence of neurologic complications and the risk factors for neurologic complications have not been reported in a large series of patients with adult spinal deformity (ASD). Existing series include a mixed patient cohort undergoing different types of spine surgery.

METHODS

Patients with ASD undergoing surgery between 2008 and 2014 were analyzed. Patients with neurologic complications were identified; demographics, operative details, and radiographic and clinical outcomes were compared. A subanalysis of those with surgical and nonsurgical (e.g., stroke) neurologic complications was performed. Statistical analysis included t tests or χ tests as appropriate and a multivariate analysis. A P value of less than 0.025 was considered significant.

RESULTS

A total of 564 patients met the inclusion criteria. The average age was 57 years. There were a total of 116 neurologic complications in 99 patients (17.6%). There were 88 surgical procedure-related neurologic complications in 77 patients (13.7%) and 28 nonsurgical neurologic complications in 28 patients (5.0%). The most common complications were radiculopathy (30%), motor deficits (22%), mental status changes (12%), and sensory deficits (12%). Revisions (odds ratio [OR] 1.7, 95% confidence interval [CI] 1.2-2.4) and interbody fusions (OR 2.1, 95% CI 1.4-3.2) were associated with an increased risk of neurologic complications. Decompression and osteotomies (including three-column osteotomies) did not increase the risk of neurologic complications. Patients with neurologic complications were not more likely to sustain other complications; however, they were more likely to undergo another operation during the follow-up period (OR 1.9, 95% CI 1.3-2.8).

CONCLUSION

The overall incidence of neurologic complications in ASD surgery was 17.6%. The incidence of surgical neurologic complications was 13.7%. There was a higher risk of neurologic complications in revision cases and in cases in which interbody fusion was required.

LEVEL OF EVIDENCE

3.

Intraoperative Neurophysiologic Monitoring for Adult Patients Undergoing Posterior Spinal Fusion

BACKGROUND

Somatosensory evoked potentials (SSEPs) and motor evoked potentials (MEPs) are frequently used to monitor neurologic function during spinal deformity surgery. The sensitivity and specificity of intraoperative neurophysiologic monitoring (IONM) in patients undergoing posterior spinal fusion (PSF) is debatable.

METHODS

A retrospective review of all patients undergoing PSF with IONM from October 2008 to December 2012 was performed. Factors including sex, operative time, and spinal levels of posterior fusion were analyzed as risk factors for intraoperative alerts.

RESULTS

A total of 784 consecutive patients who underwent PSF with IONM without any baseline deficits were analyzed. Patients included 45% men (n = 356) and 55% women (n = 428), with a mean age of 56 years. The mean procedure time was 7 hours. Intraoperative alerts were noted for 3.3% (n = 26) of patients. In this cohort, the average number of levels involved per procedure was approximately 7, ranging from 1 to 16 levels. Of all the spinal levels, the cervicothoracic region had the highest incidence of intraoperative alerts (6 of 97 cervicothoracic cases, P = 0.06). Among these patients, age (P = 0.32), sex (P = 0.66), and procedure time (P = 0.63) were not predictive factors. Four out of 26 (15%) patients had neurologic deficits despite surgeon intervention after neuromonitoring alerts.

CONCLUSIONS

SSEP and MEP changes occurred in 3.3% of patients undergoing PSF, with the highest incidence at the cervicothoracic level. Twenty-three out of 26 patients with intraoperative neuromonitoring changes had improvements in IONM signals after interventions during surgery. Further studies using larger patient numbers may be useful in establishing the utility of neuromonitoring in PSF.

Complications following spine fusion for adolescent idiopathic scoliosis

Complications following spine fusion for adolescent idiopathic scoliosis can be characterized as either intra-operative or post-operative. The most serious and feared complication is neurologic injury, both in the intra- and post-operative period. Other intra-operative complications include dural tears and ophthalmologic or peripheral nerve deficits, which may be related to positioning. Among the most common post-operative complications are surgical site infection, venous thromboembolism, gastrointestinal complications, and implant-related complications. Significant blood loss requiring transfusion, traditionally considered a known sequelae of spine fusion, is now being recognized as a "complication" in large national databases. Pediatric spine surgeons who care for patients with AIS must be thoroughly familiar with all potential complications and their management.

UHMWPE Sublaminar Wires in Posterior Spinal Instrumentation: Stability and Biocompatibility Assessment in an Ovine Pilot Study

STUDY DESIGN

An animal study.

OBJECTIVE

To explore ultra-high molecular weight polyethylene (UHMWPE) sublaminar wires in spinal surgery and to assess stability and biocompatibility of the UHMWPE instrumentation in an ovine model.

SUMMARY OF BACKGROUND DATA

Sublaminar wiring is a well-established technique in segmental scoliosis surgery. However, during introduction and/or removal of the metal sublaminar wires, neurological problems can occur. Abrasion after cutting metal wires for removal can lead to damage to the dural sac. Sublaminar wires have to withhold large forces and breakage of the wires can occur. Different types of sublaminar wires have been developed to address these problems. UHMWPE sublaminar wires can potentially substitute currently used metal sublaminar metal wires. In vivo testing and biocompatibility analysis of UHMWPE wires are recommended before clinical use in spinal surgery.

MATERIALS AND METHODS

In 6 immature sheep, pedicle screws were instrumented at lumbar level L4 and attached with titanium rods to 4 thoracolumbar vertebrae using 3- and 5-mm-wide UHMWPE sublaminar wiring constructions in 5 animals. Titanium sublaminar wires were applied in 1 animal to function as a control subject. After a follow-up period of 16 weeks, the animals were sacrificed and the spines were isolated. Radiographs and computed tomography (CT) scans were made to assess stability of the instrumentation. The vertebrae were dissected for macroscopic and histologic evaluation.

RESULTS

None of the wires had loosened and the instrumentation remained stable. CT scans and radiographs showed no signs of failure of the instrumentation and no neurological complications occurred. Although several bony bridges were seen on CT, growth was observed at the operated levels. Biocompatibility was assessed by macroscopical and histologic analysis, showing no signs of dural or epidural inflammation.

CONCLUSIONS

This pilot animal study shows that UHMWPE sublaminar wiring is a safe technique. The UHMWPE wires are biocompatible and provide sufficient stability in spinal instrumentation. Heterotopic ossification because of periost reactions in the ovine spine led to some restrictions in this study.

Reversible Intraoperative Neurophysiologic Monitoring Alerts in Patients Undergoing Arthrodesis for Adolescent Idiopathic Scoliosis: What Are the Outcomes of Surgery?

BACKGROUND

Confidence in intraoperative neurophysiologic monitoring (IONM) data can allow scoliosis surgeons to proceed with surgery even after a monitoring alert, assuming the recovery of signals. We sought to determine the outcomes of surgical treatment of adolescent idiopathic scoliosis (AIS) after a notable IONM alert.

METHODS

We identified 676 patients who underwent arthrodesis with use of IONM for the treatment of AIS. The patients were divided into 2 cohorts: those who experienced a lower-extremity IONM alert and those who did not. An alert was defined as a notable change in IONM data, specifically, a ≥50% drop in somatosensory evoked potentials (SSEPs) and/or in transcranial motor evoked potentials (tcMEPs).

RESULTS

Of the 676 patients, 36 (5.3%) experienced IONM alerts. Those patients had a larger preoperative major Cobb angle (mean of 61° ± 13° compared with 55° ± 12° for the no-alert group; p < 0.01), a greater number of levels fused (mean of 12 ± 2 compared with 11 ± 2; p < 0.01), a longer operative duration (mean of 357 ± 157 minutes compared with 298 ± 117 minutes; p < 0.01), a higher estimated blood loss (1,857 ± 1,323 mL compared with 999 ± 796 mL; p < 0.01), and a greater volume of autologous blood transfused (mean of 527 ± 525 mL compared with 268 ± 327 mL; p < 0.01). Among patients who experienced an alert and had a completed operation (34 of 36 patients), mean postoperative radiographic measurements were similar to those of the no-alert group in terms of the percentage of correction of the major Cobb angle (alert, 66% ± 13%; no alert, 64% ± 19%; p = 0.53) and of rib prominence (alert, 49% ± 36%; no alert, 47% ± 46%; p = 0.83) and measurement of thoracic kyphosis (alert, 23° ± 10°; no alert, 22° ± 2°; p = 0.58). The Scoliosis Research Society (SRS)-22 outcome scores were also similar between the 2 cohorts.

CONCLUSIONS

Notable IONM changes occurred in 5.3% of the patients who underwent arthrodesis for AIS. Those patients had larger preoperative deformity, a longer operative duration, a greater number of levels fused, a higher estimated blood loss, and a greater volume of autologous blood transfused. Return of IONM data guided the surgeon to safely complete the procedure in 34 of 36 patients, with correction similar to that of patients who did not experience an alert.

LEVEL OF EVIDENCE

Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Use of subtransverse process polyester bands in pediatric spine surgery: a case series of 4 patients with a minimum of 12 months' follow-up

OBJECT In a previous study, the authors reported on their experience with the use of sublaminar polyester bands as part of segmental spinal constructs. However, the risk of neurological complications with sublaminar passage of instrumentation, such as spinal cord injury, limits the use of this technique. The present study reports the novel use of subtransverse process polyester bands in posterior instrumented spinal fusions of the thoracic and lumbar spines and sacrum or ilium in 4 patients. METHODS The authors retrospectively reviewed the demographic and procedural data of patients who had undergone posterior instrumented fusion using subtransverse process polyester bands. RESULTS Four patients, ranging in age from 11 to 22 years, underwent posterior instrumented fusion for neuromuscular scoliosis (3 patients) and thoracic hyperkyphosis (1 patient). There were 3 instances of transverse process fracture, with application and tensioning of the polyester band in 1 patient. Importantly, there was no instance of spinal cord injury with subtransverse process passage of the polyester band. The lessons learned from this technique are discussed. CONCLUSIONS This study has shown the "Eleghia" technique of passing subtransverse process bands to be a technically straightforward and neurologically safe method of spinal fixation. Pedicle screws, laminar/pedicle/transverse process hooks, and sublaminar metal wires/bands have been incorporated into posterior spinal constructs; they have been widely reported and used in the thoracic and lumbar spines and sacrum or ilium with varying success. This report demonstrates the promising results of hybrid posterior spinal constructs that include the Eleghia technique of passing subtransverse process polyester bands. This technique incorporates technical ease with minimal risk of neurological injury and biomechanical stability.

Delayed Postoperative Neurologic Deficits in Spinal Deformity Surgery

STUDY DESIGN

A cross-sectional survey of surgeon members of the Scoliosis Research Society (SRS).

OBJECTIVE

This study sought to characterize the incidence, clinical presentation, diagnostic workup, treatment, and neurologic prognosis following delayed postoperative neurologic deficit (DPND) in patients undergoing spinal deformity surgery.

SUMMARY OF BACKGROUND DATA

DPND is a potentially devastating condition following spinal surgery, characterized by the development of a neurological deficit within hours or days of the surgical procedure. To date, only case reports and small case series have been published on the topic.

METHODS

We developed a survey to characterize DPND following spinal deformity surgery. This survey was distributed to surgeon members of the SRS through email and standard mail. The overall response rate was 38% (352/929).

RESULTS

Our results suggest an estimated DPND incidence of 1 of 9910 cases (0.01%). Eighty-one surgeons (23%) experienced at least 1 DPND in the past 10 years (92 total cases). Most common diagnoses were scoliosis (69%), kyphosis (23%), and spondylolisthesis (14%); 20% were revision surgeries. The number of hours to deficit onset was as follows: 1 to 12 (36%), 13 to 24 (27%), 25 to 48 (27%), more than 48 (10%). The most commonly cited sources of injury included ischemic injury (38%) and cord compression (15%). Forty-one percent experienced complete neurologic recovery, 26% partial, and 33% no recovery. Twenty-one percent of patients achieved final neurologic status within 1 week, 38% by 1 month, and 73% by 6 months. Patients with compression-related DPND had a significantly greater likelihood of experiencing some neurologic recovery (≥1 ASIA Grade) than ischemia-related DPND (86% versus 51%, P = 0.049).

CONCLUSIONS

DPND occurs at an estimated incidence of 0.01%. Sixty-three percent of DPND cases occurred within the first 24 hours and 90% within 48 hours. Complete (41%) or partial (26%) neurologic recovery may be expected, especially in compression-related DPND, emphasizing the need for perioperative vigilance, prompt recognition, and early intervention.

LEVEL OF EVIDENCE

4.

Biomechanics of a flexible sublaminar connector in long-segment thoracic fixation

OBJECT The Universal Clamp Spinal Fixation System (UC) is a novel sublaminar connection for the spine that is currently used in conjunction with pedicle screws at the thoracic levels for the correction of scoliosis. This device allows the surgeon to attach rods and incorporate a pedicle screw construction. The flexible composition of the UC should provide flexibility intermediate to the uninstrumented spine and an all-screw construct. This hypothesis was tested in vitro using nondestructive flexibility testing of human cadaveric spine segments. METHODS Six unembalmed human cadaveric thoracic spine segments from T-3 to T-11 were used. The specimens were tested under the following conditions: 1) intact; 2) after bilateral screws were placed at T4-T10 and interconnected with longitudinal rods; 3) after placement of a hybrid construction with screws at T-4, T-7, and T-10 with an interconnecting rod on one side and screws at T-4 and T-10 with the UC at T5-9 on the contralateral side; (4) after bilateral screws were placed at T-4 and T-10 and interconnected with rods and bilateral UC were placed at T5-9; and 5) after bilateral screws at T-4 and T-10 were placed and interconnected with rods and bilateral sublaminar cables were placed at T5-9. Pure moments of 6.0 Nm were applied while optoelectronically recording 3D angular motion. RESULTS Bilateral UC placement and bilateral sublaminar cables both resulted in a significantly greater range of motion than bilateral pedicle screws during lateral bending and axial rotation, but not during flexion or extension. There were no differences in stability between bilateral UC and bilateral cables. The construct with limited screws on one side and UC contralaterally showed comparable stability to bilateral UC and bilateral cables. CONCLUSIONS These results support using the UC as a therapeutic option for spinal stabilization because it allows comparable stability to the sublaminar cables and provides flexibility intermediate to that of the uninstrumented spine and an all-screw construct. Equivalent stability of the hybrid, bilateral UC, and bilateral cable constructs indicates that 6-level UC provides stability comparable to that of a limited (3-point) pedicle screw-rod construct.

[Comparison of propofol and midazolam on patients undergoing spinal surgery with intraoperative wake-up test: randomized clinical trial]

BACKGROUND AND OBJECTIVES

Instrumentation in correction operations for spinal deformities carries a 0.5-5% risk of injuring the spinal cord. The wake-up test is used for early detection of these injuries. In this study we compared the effects of propofol and midazolam during wake-up test in scoliosis surgery.

METHODS

Thirty patients were randomly assigned as group P and group M. Anesthesia was induced with propofol 2.5mgkg(-1) for group P or midazolam 0.5mgkg(-1) for group M with remifentanil 0.5μgkg(-1) and cisatracurium 0.15mgkg(-1) for both groups. At the maintenance of anesthesia O2/air and infusions of remifentanil and cisatracurium were used. In group P, propofol 6-10mgkg(-1)h(-1) and in group M, midazolam 0.5mgmgkg(-1) were preferred. Approximately 15min before the wake-up test, all drugs were discontinued. At the wake-up test, anesthesiologist asked the patients to open their eyes and squeeze his/her hand at every 30s until the patients responded. Then patients were told to wiggle their toes. Hemodynamic parameters, time of eye-opening, appropriate movement upon verbal command were evaluated. BIS frequency throughout the operation was recorded.

RESULTS

The eye opening time was 9±2.15min in group P and 7±3.15min in group M. Motor movement time was 12±2.55min in group P and 21.25±3.93min in group M.

CONCLUSION

Propofol provided better wake-up conditions and conducted a better neurologic assessment within the same BIS values than midazolam.

Braided tubular superelastic cables provide improved spinal stability compared to multifilament sublaminar cables

This study investigates the use of braided tubular superelastic cables, previously used for sternum closure following sternotomy, as sublaminar fixation method. It compares the biomechanical performance of spinal instrumentation fixation systems with regular sublaminar cables and proprietary superelastic cables. A hybrid experimental protocol was applied to six porcine L1-L4 spinal segments to compare multifilament sublaminar cables (Atlas, Medtronic Sofamor Danek, Memphis, TN) with proprietary superelastic cables. First, intact total range of motion was determined for all specimens using pure moment loading. Second, pure moments were imposed to the instrumented specimens until these intact total ranges of motion were reproduced. Compared to the intact specimens, the use of superelastic cables resulted in stiffer instrumented specimens than the use of multifilament cables for all the loading modes except axial torsion. Consequently, the superelastic cables limited the instrumented segments mobility more than the multifilament cables. Spinal instrumentation fixation systems using superelastic cables could be a good alternative to conventional sublaminar cables as it maintains a constant stabilization of the spine during loading.

Instrumentation of the posterior thoracolumbar spine: from wires to pedicle screws

Over the past 120 years, spinal stabilization has advanced immensely. An updated review highlighting these advancements has not been performed in the past 20 years. The objective of this report is to provide a historical assessment of the decades outlining various key innovators, their techniques, and instrumentation. It is important to provide new generations of surgeons and students with historical evidence of the value of developing new techniques and instrumentation to improve patient care and outcomes.

Adolescent idiopathic scoliosis correction achieved by posteromedial translation using polyester bands: A comparative study of subtransverse process versus sublaminar fixation

PURPOSE

Sublaminar polyester bands have been used in hybrid construct to achieve correction of adolescent idiopathic scoliosis since 2003. Despite the reported safety of the bands, some surgeons remain reluctant at the idea of approaching the canal because of the potential neurological complications reported with the Luque wiring. Sub transverse bands might be an alternative. The present study is the first to compare sublaminar polyester band fixation to fixation of polyester bands around the transverse processes in hybrid constructs used to treat AIS.

METHODS

Two cohorts of consecutive patients treated for thoracic AIS were retrospectively reviewed, with a minimum 2-year follow-up. Posteromedial translation was used for main curve correction in all cases. Sublaminar polyester bands were used in group 1 (20 patients). In group 2 (20 patients), the same implant was used, but the bands were passed around the transverse process instead of the lamina. Radiographic analysis included frontal Cobb angle measurements for each curve, thoracic kyphosis and rotation of the apical vertebra (RVA).

RESULTS

Mean operative time was similar in groups 1 and 2 (235±35 and 240±30minutes, respectively). Mean frontal correction achieved for the main curve was similar in both groups, 62.5±17.4% in group 1 and 54.1±19.4% in group 2. Sagittal correction was similar, with a final mean thoracic kyphosis of 30.9°±9.7° and 27.8°± 6.8° in group 1 and 2, respectively. Correction of RVA was similar in both groups postoperatively, 65.8% (±29.1) and 54.4% (±42.7) in group 1 and 2 respectively. No transverse process or lamina fracture was observed during insertion of the bands or curve correction in any of the groups.

CONCLUSION

This study confirms that anchorage of Universal clamps (UCs) around transverse processes is a safe and efficacious technique in both the frontal and sagittal planes, providing a useful alternative for the correction of moderate AIS. UCs attached to transverse processes can achieve correction of moderate AIS similar to that obtained with sublaminar UCs while further reducing risks of vertebral canal complications.

LEVEL OF EVIDENCE

Level IV.

The 100 Classic Papers in Spinal Deformity Surgery

STUDY DESIGN

Bibliometric review of the literature.

OBJECTIVE

To identify and analyze the top 100 cited articles in spinal deformity surgery.

SUMMARY OF BACKGROUND DATA

The field of spinal deformity surgery is an ever-growing and complex field that owes its development to the work and visions of many dedicated individuals.

METHODS

The authors searched the Thomson Reuters Web of Knowledge for citations of all articles relevant to scoliosis and spinal deformity surgery. The number of citations, authorship, year, journal, and country and institution of publication were recorded for each article.

RESULTS

The most cited article was the 2001 work by Lenke et al. describing a new 2-dimensional classification system of adolescent idiopathic scoliosis used to determine the appropriate vertebral levels to be included in an arthrodesis. The second most cited was Harrington's 1962 article describing the first instrumented method for the treatment of scoliosis. The third most cited article was the 1983 study by King et al. recommending specific vertebral levels for inclusion into spinal arthrodesis. Most articles originated in the United States (62), and most were published in Spine (32). Most were published in the 1990s (28), and the 3 most common topics, in descending order, were adolescent idiopathic scoliosis (28), spinal instrumentation (18), and surgical complications (5). Author Suk had 5 articles in the top 100 list, whereas authors Kim, Liljenqvist, Lonstein, and Weinstein had 3 each. Washington University in St. Louis had 7 articles in the top 100 list.

CONCLUSIONS

This report's identification of the 100 classic articles in spinal deformity surgery allows insight into the development and trends of this challenging subspecialty of spine surgery. Furthermore, this article identifies individuals who have contributed the most to the advancement of spinal deformity surgery and the body of knowledge used to guide evidence-based clinical decision making in spinal deformity surgery today.

Mitigating spinal cord distraction injuries: the effect of durotomy in decreasing cord interstitial pressure in vitro

STUDY DESIGN

The present study involved an in vitro examination of spinal cord interstitial pressure (CIP) during distraction before and after durotomy in three spinal cord segments obtained from five pigs.

OBJECTIVES

To determine whether durotomy can be used to decrease the elevated CIP associated with spinal cord distraction.

SUMMARY OF BACKGROUND DATA

Spinal cord distraction is a known cause of spinal cord injury. Several articles describing the pathophysiology of cord distraction injuries suggest that the underlying mechanism of injury is a microvascular ischemic event. The authors have previously described an increase in CIP with spinal cord distraction, with average pressures of 23 mmHg at loads of 1,000 g. To date, there are no published studies that have evaluated the efficacy of intentional durotomies as a treatment for elevated CIP.

METHODS

A total of 15 spinal cord sections were harvested from pigs and distracted while immersed in saline, using a fixed 1,000 g distraction force. The CIP decay was then measured at 30-s intervals for 10 min. The distraction/relaxation maneuver was performed six times with continuous CIP monitoring and was subsequently followed by durotomy.

RESULTS

The pressure-decay curves were similar for each specimen, but varied according to individual pigs and anatomical levels. CIP decayed over the first 4 min of distraction and remained constant for the final 6 min. Longitudinal durotomy led to a dramatic drop in CIP toward baseline and appeared to be as effective as transverse durotomy with regard to the normalization of pressure.

CONCLUSION

Spinal cord distraction causes elevations in CIP. Durotomy lowers elevated CIP in vitro and may be effective at lowering CIP in vivo. Further study is required to evaluate the usefulness of durotomy in vivo.

Comparison of propofol and midazolam on patients undergoing spinal surgery with intraoperative wake-up test: randomized clinical trial

BACKGROUND AND OBJECTIVES

Instrumentation in correction operations for spinal deformities carries a 0.5-5% risk of injuring the spinal cord. The wake-up test is used for early detection of these injuries. In this study we compared the effects of propofol and midazolam during wake-up test in scoliosis surgery.

METHODS

Thirty patients were randomly assigned as group P and group M. Anesthesia was induced with propofol 2.5 mg kg(-1) for group P or midazolam 0.5 mg kg(-1) for group M with remifentanil 0.5 μg kg(-1) and cisatracurium 0.15 mg kg(-1) for both groups. At the maintenance of anesthesia O2/air and infusions of remifentanil and cisatracurium were used. In group P, propofol 6-10 mg kg(-1)h(-1) and in group M, midazolam 0.5 mg mg kg(-1) were preferred. Approximately 15 min before the wake-up test, all drugs were discontinued. At the wake-up test, anesthesiologist asked the patients to open their eyes and squeeze his/her hand at every 30s until the patients responded. Then patients were told to wiggle their toes. Hemodynamic parameters, time of eye-opening, appropriate movement upon verbal command were evaluated. BIS frequency throughout the operation was recorded.

RESULTS

The eye opening time was 9 ± 2.15 min in group P and 7 ± 3.15 min in group M. Motor movement time was 12 ± 2.55 min in group P and 21.25 ± 3.93 min in group M.

CONCLUSION

Propofol provided better wake-up conditions and conducted a better neurologic assessment within the same BIS values than midazolam.

Predictive Value of Somatosensory Evoked Potential Monitoring during Resection of Intraparenchymal and Intraventricular Tumors Using an Endoscopic Port

BACKGROUND AND PURPOSE

Intraoperative neurophysiological monitoring (IONM) using upper and lower somatosensory evoked potentials (SSEPs) is an established technique used to predict and prevent neurologic injury during intracranial tumor resections. Endoscopic port surgery (EPS) is a minimally-invasive approach to deep intraparenchymal and intraventricular brain tumors. The authors intended to evaluate the predictive value of SSEP monitoring during resection of intracranial brain tumors using a parallel endoscopic technique.

METHODS

A retrospective review was conducted of patients operated on from 2007-2010 utilizing IONM in whom endoscopic ports were used to remove either intraparenchymal or intraventricular tumors. Cases were eligible for review if an endoscopic port was used to resect an intracranial tumor and the electronic chart included all intraoperative monitoring data as well as pre- and post-operative neurologic exams.

RESULTS

139 EPS cases met criteria for inclusion. Eighty five patients (61%) had intraparenchymal and fifty four (39%) had intraventricular tumors or colloid cysts. SSEP changes were seen in eleven cases (7.9%), being irreversible in three (2.2%) and reversible in eight cases (5.8%). Seven patients (5.0%) with intraparenchymal tumors had SSEP changes which met our criterea for significant changes while there were four (2.9%) with intraventricular (p-value=0.25). Five patients suffered post operative deficits, two reversible and two irreversible SSEP changes. Only one case exhibited post operative hemiparesis with no SSEP changes. The positive predictive value of SSEP was 45.4% and the negative predictive value was 99.2%.

CONCLUSIONS

Based on the high negative and low positive predictive values, the utility of SSEP monitoring for cylindrical port resections may be limited. However, the use of SSEP monitoring can be helpful in reducing the impact of endoscopic port manipulation when the tumor is closer to the somatosensory pathway.

Complications of surgical treatment of pediatric spinal deformities

Surgery in a child with spinal deformity is challenging. Although current orthopedic practice ensures good long-term surgical results, complications occur. Idiopathic scoliosis represents the most extensively investigated deformity of the pediatric spine. Nonidiopathic deformities of the spine are at higher risk for perioperative and long-term complications, mainly because of underlying comorbidities. A multidisciplinary treatment strategy is helpful to assure optimization of medical conditions before surgery. Awareness of complications that occur during or after spine surgery is essential to avoid a poor outcome and for future surgical decision making. This article summarizes the complications of surgical treatment of the growing spine.

Current concepts and controversies on adolescent idiopathic scoliosis: Part I

Adolescent idiopathic scoliosis is the most common spinal deformity encountered by General Orthopaedic Surgeons. Etiology remains unclear and current research focuses on genetic factors that may influence scoliosis development and risk of progression. Delayed diagnosis can result in severe deformities which affect the coronal and sagittal planes, as well as the rib cage, waistline symmetry, and shoulder balance. Patient's dissatisfaction in terms of physical appearance and mechanical back pain, as well as the risk for curve deterioration are usually the reasons for treatment. Conservative management involves mainly bracing with the aim to stop or slow down scoliosis progression during growth and if possible prevent the need for surgical treatment. This is mainly indicated in young compliant patients with a large amount of remaining growth and progressive curvatures. Scoliosis correction is indicated for severe or progressive curves which produce significant cosmetic deformity, muscular pain, and patient discontent. Posterior spinal arthrodesis with Harrington instrumentation and bone grafting was the first attempt to correct the coronal deformity and replace in situ fusion. This was associated with high pseudarthrosis rates, need for postoperative immobilization, and flattening of sagittal spinal contour. Segmental correction techniques were introduced along with the Luque rods, Harri-Luque, and Wisconsin systems. Correction in both coronal and sagittal planes was not satisfactory and high rates of nonunion persisted until Cotrel and Dubousset introduced the concept of global spinal derotation. Development of pedicle screws provided a powerful tool to correct three-dimensional vertebral deformity and opened a new era in the treatment of scoliosis.

Delayed Tetraplegia After Thoracolumbar Scoliosis Surgery in Stuve-Wiedemann Syndrome

OBJECTIVE

We present 2 patients with Stuve-Wiedemann syndrome (SWS) who suffered delayed tetraparesis following posterior spinal surgery for scoliosis.

BACKGROUND SUMMARY

Delayed tetraparesis after a syndromic thoracic scoliosis correction has never been reported. A cord injury distant from the surgical site is rare, and intraoperative neuromonitoring should be used to detect and prevent neurologic impairment.

METHODS

Review of medical charts.

RESULTS

Two patients with SWS suffered delayed tetraparesis 20 and 40 hours respectively after thoracolumbar posterior surgery. In one patient distal motor evoked potentials fell and recovered partially during surgery. In both patients, early postoperative neurologic examination was normal (in one of them except for the extensor hallucis 2/5). CT scan showed correct instrumentation placement and no compressive haematoma. MRI ruled out cord anomalies, but revealed in both patients identical cervical edema that was most likely secondary to ischemia. Angiogram revealed an absence of anterior cord vascular supply.

CONCLUSIONS

Correction of severe deformities in syndromic patients may lead to stretch injuries of the spinal cord and its vascular supply. This in turn may lead to a neurological deficit extending beyond the limits of the spinal instrumentation. Abrupt postoperative neck pain may be an alert to this impending development. Close surveillance in the early postoperative period should be maintained in patients with SWS because a delayed neurological deficit can be present even hours afterwards and may be cranial to the surgical level.

Validity of somatosensory evoked potentials as early indicators of neural compromise in rat model of spinal cord compression

OBJECTIVE

To determine the percentage change in somatosensory evoked potential amplitude and the duration of spinal cord compression that can be tolerated intraoperatively in a rat model before there are significant post-operative functional deficits.

METHODS

Thirty two adult male Wistar rats were divided into four groups according to the percentage of induced SSEP signal loss; all animals had pre-operative functional testing. Following surgical placement of a balloon catheter in the thoracic sub-laminar space, SSEPs were recorded while the spinal cord was compressed by inflation of the balloon. The recordings were terminated after a different percentage loss of SSEP amplitude in each group. Functional behavioral testing was repeated after 24 h.

RESULTS

Only the group wherein the catheter was left inflated for 15 min after a complete (100%) loss of SSEP amplitude showed a significant deterioration in functional testing as compared to pre-operative baseline values. Functional testing remained normal for the groups in which termination of spinal cord compression occurred immediately after a decrease of SSEP amplitude to 50% or 100%.

CONCLUSIONS

SSEP loss of up to 100% can be tolerated in a rat model of spinal cord compression as long as the compression is terminated immediately after the SSEP decrease is detected. Prolonged spinal cord compression, with concomitant SSEP decrease, can result in post-operative functional deficits despite mitigating procedures to remove the compression.

SIGNIFICANCE

This study is an important first step in providing basic science evidence for the establishment of acceptable "alarm criteria" during spinal surgery.

Use of the Universal Clamp in adolescent idiopathic scoliosis for deformity correction and as an adjunct to fusion: 2-year follow-up

PURPOSE

Among posterior surgical techniques for treating adolescent idiopathic scoliosis (AIS), hybrid constructs with pedicle-screw fixation in the lumbar spine and other anchors in the thoracic spine have been reported to provide to be of more physiological value in postoperative thoracic kyphosis than all-screw constructs. The Universial Clamp (UC) equipped with a soft sublaminar band is a relatively new thoracic anchor that can be used in hybrid constructs. A dedicated reduction tool that applies traction to the sublaminar band permits gentle translation of the thoracic curve to the precontoured fusion rods, which have been previously anchored distally by pedicle screws and proximally by hooks in a claw configuration. The aim of this study was to evaluate radiographic results of AIS treatment using UC hybrid constructs.

METHODS

This was a prospective case series in which 29 consecutive patients with Lenke type 1, 2 or 3 AIS operated on by two surgeons in two centers were followed for 24 months. Necessity for anterior release was an exclusion criterion.

RESULTS

A total of 5.4 ± 1.4 UCs were used per patient. The major thoracic curve was reduced from 55 ± 7° to 14 ± 6° at 1 month and 17 ± 6° at 24 months (correction 70%) without complications. In the patients who had less than 20° of T5-T12 kyphosis preoperatively, thoracic kyphosis improved from 14 ± 4° to 20 ± 3° at 3 months and 24 ± 9° at 24 months. In the other patients, preoperative thoracic kyphosis (27° ± 6°) was unchanged by the operation.

CONCLUSION

UC hybrid constructs appear to safely provide satisfying coronal correction while consistently improving thoracic kyphosis in patients who also have preoperative hypokyphosis. We hypothesize that diminution in thoracic kyphosis was consistently avoided due to the straightforward traction of the spine to the fusion rods into which the chosen kyphosis was contoured by the surgeon before applying the reduction tool to the sublaminar bands.

Pediatric pedicle screws: comparative effectiveness and safety: a systematic literature review from the Scoliosis Research Society and the Pediatric Orthopaedic Society of North America task force

BACKGROUND

Pedicle screws are widely used in spinal surgery. There is extensive published literature concerning the use of pedicle screw instrumentation for spinal surgery in adults. Now there is a trend to use pedicle screws in pediatric patients, including the very young. A systematic review of the current English-language literature on the use of pedicle screw instrumentation in the pediatric age group was performed to specifically determine (1) the pedicle screw placement accuracy in patients with spine deformity and (2) the effect size of all-pedicle screw constructs compared with other methods of spinal instrumentation in terms of the percentage of scoliosis correction.

METHODS

English-language studies of pedicle screw use in pediatric patients (defined as those younger than eighteen years of age) were included. Descriptive statistics synthesized the accuracy of pedicle screw placement. Accuracy rates were compared between pediatric and adult patients. The effect of pedicle screw instrumentation on scoliosis correction was calculated with use of Cobb angle measurements.

RESULTS

On the basis of the literature search, 1181 articles were screened, 320 abstracts were examined, and ninety full-text articles representing 5761 patients were reviewed in detail. Seventeen studies met the inclusion criteria for the analysis of pedicle screw placement accuracy. A total of 13,536 pedicle screws were placed in 1353 pediatric patients. The overall placement accuracy rate in pediatric patients was 94.9%, which was higher than the rate of 91.5% reported for adults. The weighted, geometric, and 5% trimmed mean accuracy rates of pedicle screw placement were 91.9%, 88.5%, and 89.1%, respectively (standard deviation = 10%; interquartile range = 10%). Sixteen comparative studies met the inclusion criteria for the analysis of the effect of pedicle screw instrumentation on scoliosis correction. Pedicle screw constructs had a significantly larger percentage of Cobb angle correction compared with hooks (Cohen's d = 1.14) and hybrid constructs (Cohen's d = 0.49).

CONCLUSIONS

The accuracy of pedicle screw placement in the pediatric spine exceeds the accuracy rate reported in adults. Pedicle screw instrumentation constructs are significantly more effective for scoliosis correction, as determined on the basis of Cobb angle measurements, than are hook constructs and hybrid constructs.

Evaluation of pullout strength and failure mechanism of posterior instrumentation in normal and osteopenic thoracic vertebrae

Object

There is limited data on the pullout strength of spinal fixation devices in the thoracic spine among individuals with different bone quality. An in vitro biomechanical study on the thoracic spine was performed to compare the pullout strength and the mechanism of failure of 4 posterior fixation thoracic constructs in relation to bone mineral density (BMD).

Methods

A total of 80 vertebrae from 11 fresh-frozen thoracic spines (T2–12) were used. Based on the results from peripheral quantitative CT, specimens were divided into 2 groups (normal and osteopenic) according to their BMD. They were then randomly assigned to 1 of 4 different instrumentation systems (sublaminar wires, pedicle screws, lamina claw hooks, or pedicle screws with wires). The construct was completed with 2 titanium rods and 2 transverse connectors, creating a stable frame. The pullout force to failure perpendicular to the rods as well as the pattern of fixation failure was recorded.

Results

Mean pullout force in the osteopenic Group A (36 vertebrae) was 473.2 ± 179.2 N and in the normal BMD Group B (44 vertebrae) was 1414.5 ± 554.8 N. In Group A, no significant difference in pullout strength was encountered among the different implants (p = 0.96). In Group B, the hook system failed because of dislocation with significantly less force than the other 3 constructs (931.9 ± 345.1 N vs an average of 1538.6 ± 532.7 N; p = 0.02). In the osteopenic group, larger screws demonstrated greater resistance to pullout (p = 0.011). The most common failure mechanism in both groups was through pedicle base fracture.

Conclusions

Bone quality is an important factor that influences stability of posterior thoracic implants. Fixation strength in the osteopenic group was one-fourth of the value measured in vertebrae with good bone quality, irrespective of the instrumentation used. However, in normal bone quality vertebrae, the lamina hook claw system dislocated with significantly less force when compared with other spinal implants. Further studies are needed to investigate the impact of different transpedicular screw designs on the pullout strength in normal and osteopenic thoracic spines.

Major neurologic deficit immediately after adult spinal surgery: incidence and etiology over 10 years at a single training institution

STUDY DESIGN

Retrospective study of adult patients who underwent spinal surgery over a 10-year period at a single institution.

OBJECTIVE

New onset postoperative paralysis remains one of the most feared complications of spinal surgery. The goal of this study was to determine the incidence and etiology of new onset major neurologic deficit immediately after adult spinal surgery.

SUMMARY OF BACKGROUND DATA

Previous studies, focusing on specific disease entities, have shown incidence rates of significant spinal cord or cauda equina injury after spinal surgery ranging from approximately 0% to 2%.

METHODS

The authors reviewed the quality assurance records for adult patients who underwent spinal surgery over a 10-year period (July 1, 1996 to June 30, 2006) by surgeons in the Department of Neurosurgery, University of Cincinnati College of Medicine at hospitals affiliated with the neurologic surgery residency program. Patients with new onset major neurologic deficit immediately after spinal surgery were identified.

RESULTS

Of 11,817 adult spinal operations, 21 patients experienced new onset major neurologic deficit immediately after spinal surgery, yielding an overall incidence of 0.178%; in the cervical spine 0.293%, thoracic spine 0.488%, and lumbar/sacral spine 0.0745%. The difference in incidence between spinal regions was statistically significant (P = 0.00343). The etiology of the neurologic deficits was confirmed with reoperation and/or postoperative imaging studies: epidural hematoma in 8 patients, inadequate decompression in 5 patients, presumed vascular compromise in 4 patients, graft/cage dislodgement in 2 patients, and presumed surgical trauma in 2 patients. Placement of spinal instrumentation was performed in 12 of 21 patients (57.1%) and was associated with a significantly higher risk of new onset major neurologic deficit immediately after spinal surgery (P = 0.022).

CONCLUSIONS

The incidence of new onset major neurologic deficit immediately after adult spinal surgery is low. Epidural hematoma and inadequate decompression were the most common etiologies in this series of patients.

Use of the Universal Clamp for deformity correction and as an adjunct to fusion: preliminary results in scoliosis

PURPOSE

Evaluation of a novel instrumentation device for adolescent idiopathic scoliosis.

METHODS

A new osteosynthesis implant (Universal Clamp) primarily consisting of a sublaminar band and titanium clamp was prospectively studied in 32 patients (average age, 15 years) with a major thoracic curve.

RESULTS

The Universal Clamp was used without anterior release to reduce and maintain correction of the thoracic curve, which improved from 55.1° preoperatively to 14.5° at 3 months without neurological complication or loss of kyphosis.

CONCLUSIONS

This implant distributes stress over a larger area of the laminar cortex than sublaminar wires, patently reducing the risk of laminar fracture for equivalent reduction forces, and permits progressive reduction at several apical levels simultaneously.